fixes #25477, downward inference of generic methods

* we now push the context return type down when inferring
* we also take this into account in our initial downards inference for arguments
* adds a common AST interface for FunctionExpressionInvocation and MethodInvocation, so we can handle these more uniformly

[email protected], [email protected]

Review URL: https://codereview.chromium.org/1720433002 .

Author: John Messerly

pkg/analyzer/lib/dart/ast/ast.dart

@@ -536,7 +536,7 @@ abstract class AstNode {
    * (either AST nodes or tokens) that make up the contents of this node,
    * including doc comments but excluding other comments.
    */
-  Iterable /*<AstNode | Token>*/ get childEntities;
+  Iterable/*<AstNode | Token>*/ get childEntities;
 
   /**
    * Return the offset of the character immediately following the last character
@@ -591,7 +591,7 @@ abstract class AstNode {
    * Use the given [visitor] to visit this node. Return the value returned by
    * the visitor as a result of visiting this node.
    */
-  dynamic /* =E */ accept /*<E>*/ (AstVisitor /*<E>*/ visitor);
+  dynamic /* =E */ accept/*<E>*/(AstVisitor/*<E>*/ visitor);
 
   /**
    * Return the most immediate ancestor of this node for which the [predicate]
@@ -3994,7 +3994,7 @@ abstract class FunctionExpression extends Expression {
  *
  * Clients may not extend, implement or mix-in this class.
  */
-abstract class FunctionExpressionInvocation extends Expression {
+abstract class FunctionExpressionInvocation extends InvocationExpression {
   /**
    * Initialize a newly created function expression invocation.
    */
@@ -4003,11 +4003,6 @@ abstract class FunctionExpressionInvocation extends Expression {
       TypeArgumentList typeArguments,
       ArgumentList argumentList) = FunctionExpressionInvocationImpl;
 
-  /**
-   * Return the list of arguments to the method.
-   */
-  ArgumentList get argumentList;
-
   /**
    * Set the list of arguments to the method to the given [argumentList].
    */
@@ -4093,12 +4088,6 @@ abstract class FunctionExpressionInvocation extends Expression {
    */
   void set staticInvokeType(DartType type);
 
-  /**
-   * Return the type arguments to be applied to the method being invoked, or
-   * `null` if no type arguments were provided.
-   */
-  TypeArgumentList get typeArguments;
-
   /**
    * Set the type arguments to be applied to the method being invoked to the
    * given [typeArguments].
@@ -4977,6 +4966,61 @@ abstract class InterpolationString extends InterpolationElement {
   void set value(String value);
 }
 
+/**
+ * The invocation of a function or method; either a
+ * [FunctionExpressionInvocation] or a [MethodInvocation].
+ *
+ * Clients may not extend, implement or mix-in this class.
+ */
+abstract class InvocationExpression extends Expression {
+  /**
+   * Return the function type of the invocation based on the propagated type
+   * information, or `null` if the AST structure has not been resolved, or if
+   * the invoke could not be resolved.
+   *
+   * This will usually be a [FunctionType], but it can also be an
+   * [InterfaceType] with a `call` method, `dynamic`, `Function`, or a `@proxy`
+   * interface type that implements `Function`.
+   */
+  DartType propagatedInvokeType;
+
+  /**
+   * Return the function type of the invocation based on the static type
+   * information, or `null` if the AST structure has not been resolved, or if
+   * the invoke could not be resolved.
+   *
+   * This will usually be a [FunctionType], but it can also be an
+   * [InterfaceType] with a `call` method, `dynamic`, `Function`, or a `@proxy`
+   * interface type that implements `Function`.
+   */
+  DartType staticInvokeType;
+
+  /**
+   * Return the list of arguments to the method.
+   */
+  ArgumentList get argumentList;
+
+  /**
+   * The expression that identifies the function or method being invoked.
+   * For example:
+   *
+   *     (o.m)<TArgs>(args); // target will be `o.m`
+   *     o.m<TArgs>(args);   // target will be `m`
+   *
+   * In either case, the [function.staticType] will be the
+   * [staticInvokeType] before applying type arguments `TArgs`. Similarly,
+   * [function.propagatedType] will be the [propagatedInvokeType]
+   * before applying type arguments `TArgs`.
+   */
+  Expression get function;
+
+  /**
+   * Return the type arguments to be applied to the method being invoked, or
+   * `null` if no type arguments were provided.
+   */
+  TypeArgumentList get typeArguments;
+}
+
 /**
  * An is expression.
  *
@@ -5519,7 +5563,7 @@ abstract class MethodDeclaration extends ClassMember {
  *
  * Clients may not extend, implement or mix-in this class.
  */
-abstract class MethodInvocation extends Expression {
+abstract class MethodInvocation extends InvocationExpression {
   /**
    * Initialize a newly created method invocation. The [target] and [operator]
    * can be `null` if there is no target.
@@ -5531,11 +5575,6 @@ abstract class MethodInvocation extends Expression {
       TypeArgumentList typeArguments,
       ArgumentList argumentList) = MethodInvocationImpl;
 
-  /**
-   * Return the list of arguments to the method.
-   */
-  ArgumentList get argumentList;
-
   /**
    * Set the list of arguments to the method to the given [argumentList].
    */
@@ -5630,12 +5669,6 @@ abstract class MethodInvocation extends Expression {
    */
   void set target(Expression expression);
 
-  /**
-   * Return the type arguments to be applied to the method being invoked, or
-   * `null` if no type arguments were provided.
-   */
-  TypeArgumentList get typeArguments;
-
   /**
    * Set the type arguments to be applied to the method being invoked to the
    * given [typeArguments].

pkg/analyzer/lib/src/dart/ast/ast.dart

@@ -5054,69 +5054,34 @@ class FunctionExpressionImpl extends ExpressionImpl
  * > functionExpressionInvocation ::=
  * >     [Expression] [TypeArgumentList]? [ArgumentList]
  */
-class FunctionExpressionInvocationImpl extends ExpressionImpl
+class FunctionExpressionInvocationImpl extends InvocationExpressionImpl
     implements FunctionExpressionInvocation {
   /**
    * The expression producing the function being invoked.
    */
   Expression _function;
 
-  /**
-   * The type arguments to be applied to the method being invoked, or `null` if
-   * no type arguments were provided.
-   */
-  TypeArgumentList _typeArguments;
-
-  /**
-   * The list of arguments to the function.
-   */
-  ArgumentList _argumentList;
-
   /**
    * The element associated with the function being invoked based on static type
    * information, or `null` if the AST structure has not been resolved or the
    * function could not be resolved.
    */
   ExecutableElement staticElement;
 
-  /**
-   * The function type of the method invocation, or `null` if the AST
-   * structure has not been resolved, or if the invoke could not be resolved.
-   *
-   * This will usually be a [FunctionType], but it can also be an
-   * [InterfaceType] with a `call` method, `dynamic`, `Function`, or a `@proxy`
-   * interface type that implements `Function`.
-   */
-  DartType staticInvokeType;
-
   /**
    * The element associated with the function being invoked based on propagated
    * type information, or `null` if the AST structure has not been resolved or
    * the function could not be resolved.
    */
   ExecutableElement propagatedElement;
 
-  /**
-   * Like [staticInvokeType], but reflects propagated type information.
-   */
-  DartType propagatedInvokeType;
-
   /**
    * Initialize a newly created function expression invocation.
    */
   FunctionExpressionInvocationImpl(Expression function,
-      TypeArgumentList typeArguments, ArgumentList argumentList) {
+      TypeArgumentList typeArguments, ArgumentList argumentList)
+      : super(typeArguments, argumentList) {
     _function = _becomeParentOf(function);
-    _typeArguments = _becomeParentOf(typeArguments);
-    _argumentList = _becomeParentOf(argumentList);
-  }
-
-  @override
-  ArgumentList get argumentList => _argumentList;
-
-  @override
-  void set argumentList(ArgumentList argumentList) {
-    _argumentList = _becomeParentOf(argumentList);
   }
 
   @override
@@ -5149,14 +5114,6 @@ class FunctionExpressionInvocationImpl extends ExpressionImpl
   @override
   int get precedence => 15;
 
-  @override
-  TypeArgumentList get typeArguments => _typeArguments;
-
-  @override
-  void set typeArguments(TypeArgumentList typeArguments) {
-    _typeArguments = _becomeParentOf(typeArguments);
-  }
-
   @override
   accept(AstVisitor visitor) => visitor.visitFunctionExpressionInvocation(this);
 
@@ -6166,6 +6123,55 @@ class InterpolationStringImpl extends InterpolationElementImpl
   void visitChildren(AstVisitor visitor) {}
 }
 
+/**
+ * Common base class for [FunctionExpressionInvocationImpl] and
+ * [MethodInvocationImpl].
+ */
+abstract class InvocationExpressionImpl extends ExpressionImpl
+    implements InvocationExpression {
+  /**
+   * The type arguments to be applied to the method being invoked, or `null` if
+   * no type arguments were provided.
+   */
+  TypeArgumentList _typeArguments;
+
+  /**
+   * The list of arguments to the function.
+   */
+  ArgumentList _argumentList;
+
+  @override
+  DartType propagatedInvokeType;
+
+  @override
+  DartType staticInvokeType;
+
+  /**
+   * Initialize a newly created invocation.
+   */
+  InvocationExpressionImpl(
+      TypeArgumentList typeArguments, ArgumentList argumentList) {
+    _typeArguments = _becomeParentOf(typeArguments);
+    _argumentList = _becomeParentOf(argumentList);
+  }
+
+  @override
+  ArgumentList get argumentList => _argumentList;
+
+  @override
+  void set argumentList(ArgumentList argumentList) {
+    _argumentList = _becomeParentOf(argumentList);
+  }
+
+  @override
+  TypeArgumentList get typeArguments => _typeArguments;
+
+  @override
+  void set typeArguments(TypeArgumentList typeArguments) {
+    _typeArguments = _becomeParentOf(typeArguments);
+  }
+}
+
 /**
  * An is expression.
  *
@@ -6959,7 +6965,8 @@ class MethodDeclarationImpl extends ClassMemberImpl
  * > methodInvocation ::=
  * >     ([Expression] '.')? [SimpleIdentifier] [TypeArgumentList]? [ArgumentList]
  */
-class MethodInvocationImpl extends ExpressionImpl implements MethodInvocation {
+class MethodInvocationImpl extends InvocationExpressionImpl
+    implements MethodInvocation {
   /**
    * The expression producing the object on which the method is defined, or
    * `null` if there is no target (that is, the target is implicitly `this`).
@@ -6979,32 +6986,6 @@ class MethodInvocationImpl extends ExpressionImpl implements MethodInvocation {
    */
   SimpleIdentifier _methodName;
 
-  /**
-   * The type arguments to be applied to the method being invoked, or `null` if
-   * no type arguments were provided.
-   */
-  TypeArgumentList _typeArguments;
-
-  /**
-   * The list of arguments to the method.
-   */
-  ArgumentList _argumentList;
-
-  /**
-   * The function type of the method invocation, or `null` if the AST
-   * structure has not been resolved, or if the invoke could not be resolved.
-   *
-   * This will usually be a [FunctionType], but it can also be an
-   * [InterfaceType] with a `call` method, `dynamic`, `Function`, or a `@proxy`
-   * interface type that implements `Function`.
-   */
-  DartType staticInvokeType;
-
-  /**
-   * Like [staticInvokeType], but reflects propagated type information.
-   */
-  DartType propagatedInvokeType;
-
   /**
    * Initialize a newly created method invocation. The [target] and [operator]
    * can be `null` if there is no target.
@@ -7014,19 +6995,10 @@ class MethodInvocationImpl extends ExpressionImpl implements MethodInvocation {
       this.operator,
       SimpleIdentifier methodName,
       TypeArgumentList typeArguments,
-      ArgumentList argumentList) {
+      ArgumentList argumentList)
+      : super(typeArguments, argumentList) {
     _target = _becomeParentOf(target);
     _methodName = _becomeParentOf(methodName);
-    _typeArguments = _becomeParentOf(typeArguments);
-    _argumentList = _becomeParentOf(argumentList);
-  }
-
-  @override
-  ArgumentList get argumentList => _argumentList;
-
-  @override
-  void set argumentList(ArgumentList argumentList) {
-    _argumentList = _becomeParentOf(argumentList);
   }
 
   @override
@@ -7049,6 +7021,9 @@ class MethodInvocationImpl extends ExpressionImpl implements MethodInvocation {
   @override
   Token get endToken => _argumentList.endToken;
 
+  @override
+  Expression get function => methodName;
+
   @override
   bool get isCascaded =>
       operator != null && operator.type == TokenType.PERIOD_PERIOD;
@@ -7087,14 +7062,6 @@ class MethodInvocationImpl extends ExpressionImpl implements MethodInvocation {
     _target = _becomeParentOf(expression);
   }
 
-  @override
-  TypeArgumentList get typeArguments => _typeArguments;
-
-  @override
-  void set typeArguments(TypeArgumentList typeArguments) {
-    _typeArguments = _becomeParentOf(typeArguments);
-  }
-
   @override
   accept(AstVisitor visitor) => visitor.visitMethodInvocation(this);